mineral

Likely raw tourmaline (black schorl)

Schorl tourmaline, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Black to very dark green, vitreous-to-resinous luster, commonly elongated and striated with a trigonal crystal structure; Mohs hardness 7–7.5, no prominent cleavage, specific gravity about 3.1–3.3. The pictured piece appears rough and possibly partly broken or weathered.

Identified August 25, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in granite pegmatites and hydrothermal veins when boron-rich fluids crystallize; specimens range from Precambrian to recent geological settings. Exact identification requires tests or analytical examination because dark amphibole and other minerals can look similar.

Uses & applications

Used as a gemstone when transparent and well-formed, in mineral specimens, and occasionally in scientific or electrical applications due to tourmaline’s piezoelectric and pyroelectric properties.

Geological facts

Schorl is the most common tourmaline variety and is strongly pleochroic in thin sections. Heating or pressure can produce electrical charges on its ends.

Field identification & locations

Look for a prismatic, lengthwise-striated form, high hardness, dark color, and possible attraction only if iron-rich inclusions are present; avoid relying on appearance alone. Common sources include Brazil, Afghanistan, Pakistan, Namibia, Madagascar, and the United States.